Got it!

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

The real downside to the Slant, and other old Mopar engines, is the short water pump height. If there were another couple inches, it would be interesting to experiment with more modern pumps. There are some really nice, compact, and presumably efficient pumps out there...but they all tend to be taller than the old pumps.

I agree that Slants don't have a reputation for running hot; keep in mind I'm running these things in road course endurance racing. If you're not cornering or braking, you're pretty much at full throttle all the time, for hours at a time. Our 1973 block, which raced as hot as 230, never really got above 200 or 210 on the street. And if part of the problem is reduced coolant flow above 3000 RPM, I doubt you'd see much of an impact if you're just going to the grocery store.

I don't suspect blockage to be the problem in this block, either. We saw very healthy water flow out of the top hose at lower RPMs. The "hot block" in question is the top photo in my first post; there's some surface rust because we have to race with straight water, and we found a little bit of crud at the bottom of the water jacket when we popped out the plugs, but I'd expect our (much cooler) original 1964 engine had about the same crud. We never had that '64 block cleaned out when we rebuilt it, and it raced at much lower temperatures. The really crusty '66 block in the 3rd picture is a spare that we've never actually used.

One possibility we need to look at once this new engine is installed and running is the lower hose collapsing and choking off supply to the pump. That would absolutely cause cavitation. We're using the same lower hose setup we've been running for a long time, on multiple engines: a silicon hose elbow coming off our big aluminum radiator's outlet, to a rigid union, to the upper half of a stock rubber lower radiator hose. I suppose it's possible that this hose has degraded over time, but it would be highly coincidental for the hose to start collapsing right when we switched to a new engine.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Does the hose have a spring in it?

This only happens if your radiator is much more waterflow-restrictive than it should be (i.e., clogged or severely underspecified) and the system isn't pressurised. That thing about a spring being needed in the lower hose is a myth.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

This all very interesting. Since engine rebuild two years ago including water pump replacement this engine has seemed to run hotter than before its rebuild. The old pump, well seasoned probably 20 years was working fine, but while at it I replaced it.

Now this has got me to thinking, is the new pump doing the job? I don't see much flow through radiator, and heater hoses that also feed the under carburetor hot spot as well as heater core never feel like there is much coolant in them when engine is up to temperature and running. A few weeks ago I pulled the engine to remedy a timing cover oil leak, and while refilling and purging cooling system, it seemed coolant was not circulating very much. The day was in the mid forty's, temperature gauge never made it to 12 o'clock normal with a 195* stat. I wrote it off to not enough load to heat her up. A few day later, checked coolant level, went for a drive thinking it would burp some air, and I could top it off. No burp, level was same after getting it up to normal. I have been driving it, and temperature while under way is normal, but in traffic, and sitting in park idling gauge leans to right as if it is getting hot.

This current behavior is what I would see on a day in the mid 80's, not mid 50's.

I may have replaced pump with a Gartes unit, don't remember; but generally buy the name brand at Rock Auto. My block is a 1968, and don't recall how the water pump's casting cavity is formed. The pump removed, which I still have was a six vain, and the replacement also a six vain, as i recall matching the two up at the time of installation.

The old pump looks as if the impeller is seated a mm or so below its shaft, which would increase sapcing from block. There is about 1 mm space between vaines and metal plate on pump body side .

When I got this engine running for cam brake in after rebuild it was running extremely hot, after 500 miles of driving she cooled down enough so maintaining high idle a light was not necessary to keep gauge out of hot zone. Every one said the engine was tight from rebuild, and need some brake in miles, I wonder if the pump is wrong. Are these pumps are rotation specific?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

After a little more thinking about this pump thing I took a look at the 1967 Dart FSM cooling chapter. Page 7-5. Fig. 5, 170 - 225 CI engine water pump is shown. It looks to be the cast iron impeller type favored by Dan, and is of a similar design the above aftermarket manufacturer copied with a solid disk integral to impeller facing engine block casting. Same goes for the V8 pump.


It looks as if the cast iron impeller took up more space in block casting cavity disallowing excessive coolant flow between impeller and engine block. That I suspect would improve pumping efficiency.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

A "Gates" water pump isn't a name-brand part like you have in mind. See here and here (assuming those links work, which they might not; looks like the site database is having a new kind of meltdown today)

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

In trying to picture the flow pattern in this area, I am wondering about something.

In a radial compressor (turbo/centrifugal supercharger), you don't want the incoming air to get around behind the impeller but rather to gradually 'bunch up' (hence, compress) against the wall of the housing until it reaches the outlet. Therefore, the impeller needs to fit closely against the back of the housing.

However, this pump is dealing with a liquid instead of a gas (assuming no cavitation). Since the incoming flow won't compress, would a tight fitting impeller cause the flow to slow or stall at the top of the scroll, just after the outlet?
The gradual enlargement of the scroll shape probably keeps things moving but it seems like if some water gets behind the impeller it would simply move toward the outlet without negatively impacting the flow.

I have no test data on this but am simply trying to picture what is happening in there.
I have looked at these shapes for years without ever asking "Why?", so I might as well try to learn.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

Lookie what I found, Dan's cast iron favorite:

Repair kit for original water pump I wonder if that would retro fit to a newer casting aftermarket unit? Looks to be an Oz company, not too handy to USA and killer shipping.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

While I agree modern water pumps are lousy in several ways, I hate to see people get too worked up over tracking down old-style parts at great expense. It bears further investigation but there's a lot of evidence that even a crummy modern pump still works well from a flow standpoint.

As for my modern Gates pump (which was new in the trunk of the car when I bought it so I used it), it's already leaking after about 600 miles of gentle break in use. I'm currently in the stages of trying to ignore it until it stops leaking or my interest in changing it out gets greater.

...why, it's the very same repair kit I linked up above in this very thread! Where's that been hiding?
Bakelite.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks for your thoughts, Joe. Food for my thoughts... Only way to know for Frank's situation is to try a different/modified pump. I would probably weld a plate on the back of the steel vanes, as Greg already suggested.

The only time I had a marginal experience with cooling due to the water pump (besides failure) was when I cut every other vane off a new 6-vane aftermarket pump. It worked great in almost all conditions, but I found it would get hot if idling for a while (sensible), and when pulling up steep mountains out West at 3500+ RPM. Stock replacement pump got rid of both issues.

Lou

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Home of Slant6-powered fun machines since 1988

Under the heading "other stuff", I converted over to an electric pump with a speed control system that also controls the fan with various set points. that being the case, I got to ditch my OEM WP and free up some space and allow other accessory configurations.. I plumbed the electric pump into the back side of the cavity in the OP's first pic series. I was not comfortable with the water flow path/characteristics that would present, so I formed up a billet nylon water divertor for less turbulent flow, and dead space. Its not on the road yet, so i have no idea what the end result will be.
Still haven't figured out how to post pics, here so a verbal description is all i can share.

Is that a Davies Craig water pump setup? Or some other brand?

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